Sectional doctor blade holder



March 3, 1964 R. E. CARVlLL 3,122,767

SECTIONAL DOCTOR BLADE HOLDER Filed July 23, 1962 United States Patent 3,122,767 SEQTIQNAL DGCTOR BLADE HQLDER Richard E. Carr/ill, Westwood, Mass, assignor to Bird Machine Oompany, South Walpole, Mass, a corporation of Massachusetts Filed July 23, 1962, Ser. No. 211,738 4 Claims. (Cl. l5-236) The present invention relates to doctors for roll stock, such as for paper stock as it passes over the rolls of the dryer section. Particularly, the invention relates to a novel construction {for the holders of the doctor blades of such doctors.

inasmuch as roll-forming machines for paper and the like vary widely in transverse dimension or width of the stock being processed, it has in the past been the practice to custom-make the doctor, including the holder, to the full length required. This practice involves numerous disadvantages, such as the difiiculty of machining such long lengths, which may be 200 to 300 inches long or longer, within the close tolerances required, the great inconvenience of handling and shipping, with damage often resulting, difiiculties of installation, etc.

In view of these dimculties it has been proposed in the past to make the doctor holder in shorter length sections which are installed in end-butted relation on the doctor support. However, to provide and maintain in this way the required exact alignment and abutment of the sections is difficult or impossible in many cases, primarily because of dependence on uniform registration between the sections and the support mounting. Irregularities in the support such as surface irregularities or warping, misalignment or oversize of bolt holes, etc., are apt to be refiected in disalignment of the holder sections, or to require corrective operations on the support to avoid it. Since doctor holders are frequently supplied for mount ing on old supports or supports provided by the mill, the problem is not readily controllable by the doctor support mmufacturer. In addition, loosening of a single attachment to the support may readily result in dis-alignment A of a holder section in which it occurs with other sections. These difiiculties become accentuated if it is attempted to sectionalize the holder into short lengths, such as three feet more or less, which can be readily handled and shipped.

The object of this invention is to provide a doctor blade holder construction in short lengths which can be readily assembled to a support in the field with the sections lastingly held in the exact alignment required without dependence upon exact registry of holder and support surfaces and attachment bolt holes.

in order to carry out the objective of the invention, it was conceived that if the sections of the holder were lapped rather than merely abutted and the lapped portions fastened together, better and more permanent alignment of sections would be obtainable. Initially this conception was embodied in a two superimposed part holder as shown in FIGS. 1-3 of Scott US. Patent No. 2,890,- 473, except that the upper part or bar of the holder was made shorter than the lower at one end and correspondingly longer than the lower bar at the other end, so that the top bar of one section would overlap the bottom bar of the next, and could be fastened thereto by screws to hold the sections together. This construction was a substantial improvement over merely butting sections since the doctor holder manufacturer could accurately control the registry of the mating surface of the lapped portions and further, the sections were positively held together by fasteners apart from the support attachment bolts.

However, this lapped construction did not adequately fulfill the objectives of this invention for several reasons. Since the bottom bar of each section rested on the doctor support, irregularities in the support surface could still result in disalignmen t of the holder sections. This potentiality was further accentuated by the fact that the upper and lower bar portions of the holder overlying the support were coextensive so that the bolts or screws fastening the holder to the support passed through both bars. Thus, the force of these larger fasteners tended to overcome the alignment initially obtained by the fastening of the lapped portions, if there were irregularities in the support surface as between adjacent holder sections or if there were misalignment between bolt or screw receiving holes in the support for adjacent sections.

The present invention resulted from the discovery that the difficulties mentioned with the last named construction could be overcome by revising the construction of the sections so that the bottom portion or bar of the holder no longer rested on the support but was suspended over the edge thereof by its fastenings to the upper bar, the upper bar projecting sufficiently laterally beyond the lower to be attached to the support by means of screws or bolts passing through the laterally projecting portion of the upper bar only and not through the lower bar. With this construction it has been found that the misaligning effect of support irregularities is minimized. This appears to be due in part to the fact that disalignment of support attachment screw holes has less tendency to disalign sections when the screws pass through only one of the two sections and, further, to the fact that imperfections in the support have, to a substantially lesser degree, a tendency to affect the alignment of the doctor holder sections.

The accompanying drawing illustrates a preferred embodiment of the invention wherein:

FIG. 1 is a cross-sectional view of a doctor blade holder section according to the present invention, together with doctor blade and keep and spring plates associated therewith to retain the blade resiliently and removably in the holder.

FIG. 2 is an exploded perspective view, partially cut away, of the parts of the sectional holder, blade and retaining parts shown in cross-section in FIG. 1.

FIG. 3 is a schematic plan view illustrating the manner in which doctor blade holder sections according to this invention may be assembled to the doctor support.

FIG. 4 is a fragmentary perspective view of a modified structure of one of the holder bars of FIGS. 1-3.

The embodiment chosen to illustrate the invention is similar to that of the aforesaid Scott Patent 2,890,473 in that the doctor blade holder is adapted to receive a spring plate and a keep plate bearing on the blade, this assembly being particularly advantageous in doctor action. However, the invention can be embodied in other forms as will hereinafter appear, the invention being concerned with the doctor holder itself and not with the particular arrangements by which the blade is retained in the holder.

Referring to the drawing and first particularly to FIGS. 1 and 2, the doctor shown comprises a doctor blade 10, a spring plate 12 bearing on the upper surface of the doctor blade, a keep plate 14 of smaller width than the spring plate and bearing on the doctor blade under and to the rear of the forward part of the spring plate, and a doctor blade holder designated generally at 16, by which the assembly of doctor blade, spring plate and keep plate are held so that the edge of the doctor blade is presented in close proximity to the material being doctored passing over a drum, partially indicated at 18 in FIG. 1, rotating in the direction of the arrow. The doctor blade holder is mounted on a support 20 so that the blade projects laterally from one side of the holder in a plane substantially parallel to the axis of drum 18.

The doctor blade holder is made of two transversely overlapped sections disposed in parallel planes through which the drum successively passes. The section 22 in the first of these planes is called the upper base bar and V the other section 24 the lower base bar.

The lower base bar is provided in its upper face exposed toward bar 22 with a first longitudinal groove 26 adjacent the edge thereof nearest the drum having a rearward notch 27, and a second longitudinal groove 28 spaced inwardly of bar 24 from the groove 26 and having a rearward notch 2?. Groove 26 receives lugs 3h which may be provided by rivets projecting from the opposed face at the rear edge of doctor blade iii, to retain the blade against lateral movement with its rear edge seated against the rear edge or" notch 27. Groove 28 receives tabs 32 punched or pressed from spring plate 12 to project from the opposed face and edge of the plate through registering apertures 34 adjacent the rear edge of keep plate 14, thus functioning to retain both the spring plate and the keep plate against lateral movement with their rear edges seated in notch 29.

Groove 26 and notch 27 are, as shown, preferably located in a plane further removed from the opposed face of bar 22 than are groove 28 and notch 2.

The base bars are secured together by locking screws 36 passing through an aperture 38 in bar 24 and a registering threaded aperture 39 in bar 22, and having their heads countersunk in an enlargement in the apertures 33 in the lower bar. The arrangement is such that the front edge or nose of bar 22 overlies and engages the rear portion of spring plate 12 up to a point between grooves 28 and 26, thereby locking both the spring and keep plates in position and through the pressure of these plates on the rear portion of the doctor blade 10, also resiliently loclc'ng the doctor blade in place.

In the construction disclosed in the aforesaid Scott patent the upper base bar overlaps the lower bar for the full width of the former. With this arrangement, the doctor support underlies both bars and attachment screws or bolts for fastening the assembly to the support pass through both base bars of the holder. For purposes of the present invention, however, the structure has been changed and upper base bar 22 projects rearwardly beyond the rear edge of bar, 24 a sufiicient distance to provide a support attaching lip 40. Lip 44) seats directly on the upper face of the doctor support 29 while bar 24 is disposed entirely forwardly of the front edge of the support, being suspended there by its attachment to bar 22. The assembly is attached to doctor support by screws or bolts, shown as screws 42, passing through an aperture 44 in lip iii, and a registering threaded aperture 45 in support 26.

Referring now to FIG. 3, according to the invention, the doctor blade holder bars are made of a multiplicity of short lengths, which may be of the order of 36 inches long, more or less. The bars are, however, so proportioned that when they are secured together by screws 36, one of the two bars in each section projects longitudinally beyond the other in a predetermined relationship. In one end section, shown at the left hand end of FIG. 3, bar 22 is made longer than bar 24 so that when the two bars are joined together with their left hand ends aligned, the right hand end of bar 22 extends a predetermined distance, indicated at 50, beyond the corresponding end of bar 24. The opposite end section at the top of FIG. 3 has the reverse arrangement, that is, bar 22 is made shorter than bar 24 so that when they are secured together so that their right hand ends coincide, bar 24 projects longitudinally beyond bar 22 a predetermined distance indicated at 52. The intermediate sections are made so that when they are secured together, at one end, the left hand end in FIG. 3, bar 24 extends longitudinally beyond bar 22 as indicated at 54, while the right hand end of bar 22 extends longitudinally beyond the right hand end of bar 24, as indicated at 56. The extension of each bar beyond the other at one end matches exactly the extension of the other bar beyond the other end of the next succeeding section. By making the over-extending lengths 'of one bar relative to the other in each section uniform,

that is, lengths 50, 52, 54 and 55 the same, the top and bottom bars of all the sections between the end sections may be made of the same length, thus facilitating the manufacturing process.

The exten of overlap in the longitudinal direction of the top and bottom bars is important in that it is by means of this overlap that the sections can be secured together in exact alignment which the manufacturer can control. Preferably, the extent of overlap is such that at least two fasterdng screws 36 extend through each longitudinally overlapped portion. In the construction shown, using 36 inches as the length of intermediate sections, 'an overlap of about 6 inches at each'end has been found sulficient, this providing two registering screw holes 38 and 3% in each overlapped portion with the screw holes arranged at 3 inch intervals.

To accommodate cylinders of varying length, one of the end sections of the holder may be provided in variant lengths and/ or one or more intermediate sections may be provided in different lengths, as is required to enable the assembled holder length to match the custom length required for the particular cylinder involved. Preferably, one end section is made of standard length, for example 42 inches long (36 inches overlap plus 6 inch pro jection), the intermediate sections about 36 inches long and of uniform length or with one of custom length, and

one end section of custom length.

It has been found that the short lengths of base bar portions of the holder as herein provided may be machined with great accuracy, much greater than is possible with holders made in full, half, or even third or quarter lengths. It will also be noted that the overlapping portions of the bars in each section meet in a plane on their opposed surfaces lying between notch 29 and the rear edge of bar 24, making it simple to provide exact matching. Preferably, the bars 22 and 24 of each section are secured together by screws before shipment so that each section can be checked by the manufacturer, and to facilitate ease of shipment and installation.

Installation of the sectional doctor holder of this invention has been found to be so simplified as to be readily accomplished by one man, whereas at least two were formerly required. The short sections, of which the bars are normally made of steel or bronze, are not too heavy to be handled by one installation man. To install the holder, he may start with one end section, loosely attaching it to the support 29 by means of screws 42, through screw holes 44 and 45. An intermediate section is next similarly attached to the support so that its projecting bar portion 54 or 56, overlapping or underlapping the projecting portion 5% or 52 of the end section, registers therewith, and screws 36 are fastened through the registering screw holes 38 and 3? in the overlapped portions. The insertion of a key such as a short length'of rod in the slots 26 of the lower base bars 24- of the two sections, so that the key overlaps the joint between the two sections, has been found to aid in securing proper alignment between the sections.

Each intermediate section is then installed and joined to the preceding one in the same way, until finally the other end section is reached and similarly installed. The assembly may then be checked for alignment, the screws 42 may be tightened, and the assembled and mounted holder, again checked for alignment, is ready for insertion of the doctor blade and the spring keep plates.

The embodiment of FIGS. 1-3 is constructed for endwise assembly of the spring and keep plates and the doctor blade to the holder. That is, the spring and keep plates are first assembled so that tabs 32 extend through apertures 34, and the assembly is then slid endwise between holder bars 22 and 24 with tabs 32 sliding in groove 28. An end of the doctor blade is then inserted between the end of bar 24 and the spring and keep plates, so that lugs 3%? are aligned with groove 26 and the blade is slid longitudinally of the holder into position, lugs 39 sliding in groove 26. The plates and blade may then be locked in place by cotter pins fastened through holes tl provided in each end section of the holder and corresponding holes (not shown) in the ends of the plates and doctor blade. Removal of the doctor blade and/ or spring and keep plates may be made in reverse manner, without disturbing the doctor blade holder.

Where insertion and removal of the spring and keep plates and the doctor blade from the front is necessary or desirable, the lower base bar of the doctor blade holder is provided with the modified structure shown in FIG. 4. As shown in this figure, the bar 24 is provided with slots 26', 2 and notches 27', 29', as in the embodiment of FIGS. 1-3. However, the portion of the bar in front of groove 26' is provided with slots 62 extending transversely therethrough, each sufficiently wide and deep to freely accommodate one of the lugs projecting from beneath the rear edge of the doctor blade. Two such slots may be provided for each lug 39, arranged so that when the doctor blade is in final position with respect to the holder, each lug St is disposed equidistantly between each slot 62 of a corresponding pair. Similarly, the portion of bar 24' in front of groove 23' is provided with transverse slots 64 therethrough, each of a width and depth to freely accommodate one of the tabs 32 which project from the underside of the rear portion of spring plate 12 through the apertures 34 in keep plate 14. Two slots 64 may be provided for each tab 32, arranged in the same manner as slots 62.

To assemble the plates and doctor blade from the front to a holder having the modified bar structure of E6. 4, the spring and keep plates are assembled into position so that each of the tabs 32 registers with one of the slots 64-, the assembly being pushed widthwise between the holder bars, tabs 32 sliding in slots 64- until they enter groove 255. The plates are then slid to the right or left endwise the small distance required to bring them to correct final position and are fastened by cotter pins. The same procedure is followed in assembling the doctor blade between the plates and bar 24'. To disassemble, the reverse procedure is followed, the provision of two slots 62 or 64 for each lug 3%) or tab 32 permitting the blade or plates to be slid a small distance in either direction to provide registry with one slot of each pair for removal.

It will be understood that the doctor blade, keep plate and spring plate may all be provided as usual in full length, that is, in length equal to the width of the surface to be doctored and approximately equal to the length of the holder. The spring and keep plates will normally be made of steel or bronze, while the doctor blade may be of steel, bronze, plastic or plastic-fibre composition or other suitable material.

The sectionalized doctor blade holder of this invention has been found to possess numerous advantages over the one-piece or even sectionalized holders of the prior art as mentioned above. In short lengths it is easy to machine the bars to very close tolerances so that exactitude of alignment of the bars comprising each section can be assured. The short lengths, of course, are more readily and inexpensively handled and shipped and, more importantly, the inevitable shocks and jars encountered in shipment and handling are much less apt to produce damage to the shorter sections, and if damage occurs, it is far more easily corrected. In use, if excess wear or damage occurs, it is only necessary to replace the particular section or sections affected. To this end, the user may at low cost stock one or more extra sections for replacement purposes.

Since the longitudinally overlapping portions of the top and bottom base bars do not rest on the support but are suspended therefrom, the alignment of the sections is substantially independent of the support mounting, being governed instead by the matching of the overlapping parts and the action of screws 36, which can be accurately controlled by the manufacturer. Thus, inaccuracies of registration of lip 4% with the surface of support 2a? or of screws 42 and screw-holes 44 with support scr w holes 45 are unlikely to be reflected in misalignment of the sections.

While the horizontally divided, two-part holder construction of the illustrated embodiment is preferred, together with the spring and keep plates for retaining the doctor blade, this is not essential. The advantages of this invention can be obtained, at least in part, with onepiece doctor holders which are formed as short sections with mating, longitudinally overlapping portions which do not rest on the doctor support and which are adapted to be secured together in situ independently of the mounting attachment to the doctor support and without supporting contact of the overlapped portions with the support. Further, the spring and keep plate arrangement for retaining the doctor blade in the holder is desirable but other arrangements may be used.

I claim:

1. A doctor blade holder comprising a plurality of holder sections adapted to be assembled end to end to form the complete holder, said sections being of bar-like form, each having a doctor blade edge receiving recess extending along one side thereof, and at one end thereof a longitudinally extending portion adapted to receive in lapped relation another longitudinally extending portion at the opposed end of the next succeeding section, said portions each having at least one fastening receiving aperture arranged to register with a corresponding aperture in the lapping portion of the next succeeding section for securing said sections together, said portions and said apertures being correspondingly aligned with respect to said sections so that said sections are in longitudinal alignment when said portions and apertures are in registry, each of said sections having at the opposite side from said recess a lateral extension for mounting said sections on a support so that said lapped portions of the sections are spaced outwardly of the support.

2. A doctor blade holder as claimed in claim 1 wherein said holder comprises a pair of end sections having a said longitudinally extending portion at one end only thereof, and a plurality of intermediate sections having said longitudinally projecting portions at each end thereof.

3. A doctor blade holder according to claim 2 wherein said sections are comprised of a pair of bar members secured together in lapped relation with one of said members projecting laterally beyond the other to form said lateral extension, one of said members being longer than the other in each end section to provide said longitudinal extension thereof, said bars of said intermediate sections being secured together in longitudinally staggered relation to form said longitudinally extending portions at each end thereof.

4. A doctor blade holder according to claim 1 wherein said sections are comprised of a pair of bar members secured together in lapped relation with one of said members projecting longitudinally beyond the other to form the said longitudinally extending portion and with one of said members projecting laterally beyond the other to form said lateral extension.

References Qited in the file of this patent FOREIGN PATENTS 298,519 Switzerland July 16, 1954 

1. A DOCTOR BLADE HOLDER COMPRISING A PLURALITY OF HOLDER SECTIONS ADAPTED TO BE ASSEMBLED END TO END TO FORM THE COMPLETE HOLDER, SAID SECTIONS BEING OF BAR-LIKE FORM, EACH HAVING A DOCTOR BLADE EDGE RECEIVING RECESS EXTENDING ALONG ONE SIDE THEREOF, AND AT ONE END THEREOF A LONGITUDINALLY EXTENDING PORTION ADAPTED TO RECEIVE IN LAPPED RELATION ANOTHER LONGITUDINALLY EXTENDING PORTION AT THE OPPOSED END OF THE NEXT SUCCEEDING SECTION, SAID PORTIONS EACH HAVING AT LEAST ONE FASTENING RECEIVING APERTURE ARRANGED TO REGISTER WITH A CORRESPONDING APERTURE IN THE LAPPING PORTION OF THE NEXT SUCCEEDING SECTION FOR SECURING SAID SECTIONS TOGETHER, SAID PORTIONS AND SAID APERTURES BEING CORRESPONDINGLY ALIGNED WITH RESPECT TO SAID SECTIONS SO THAT SAID SECTIONS ARE IN LONGITUDINAL ALIGNMENT WHEN SAID PORTIONS AND APERTURES ARE IN REGISTRY, EACH OF SAID SECTIONS HAVING AT THE OPPOSITE SIDE FROM SAID RECESS A LATERAL EXTENSION FOR MOUNTING SAID SECTIONS ON A SUPPORT SO THAT SAID LAPPED PORTIONS OF THE SECTIONS ARE SPACED OUTWARDLY OF THE SUPPORT. 